The present disclosure relates to a gas turbine engine, and more particularly to a method of starting an auxiliary power unit with a combustor warm-up cycle.
A start sequence for a gas turbine engine, for example, one used in an auxiliary power unit (APU), coordinates engine speed, ignition and fuel delivery to achieve a reliable start. A starter motor is coupled to the gas turbine engine and is operated to produce rotation thereof. As the starter motor accelerates the engine, a fuel delivery pump provides fuel flow thereto. Igniters are then actuated to effect ignition in a combustor section. Upon successful ignition, and once the engine has reached a self-sustaining speed, the starter motor is disengaged or operated as a generator.
Under some conditions such as high altitudes, cold temperatures or combinations thereof, the gas turbine engine may flame-out. At the extremes of altitudes and cold inlet air temperatures, the likelihood of a start failure increases.